Naoyuki Nakagawa

High-frequency magnetic properties of (FeCoNbB)-(SiO2) nanocolumnar films

(FeCo)-(SiO2) nanogranular films in which magnetic metal particles form nanosized columns, nanocolumnar, were studied. The nanostructure was formed by controlling the composition ratio of magnetic metal and insulating oxide. Inducing uniaxial anisotropy in the film plane resulted in high permeability in the GHz band and a high ferromagnetic resonance frequency. To improve the permeability loss factor, crystallinity of FeCo was controlled by adding B and Nb. As a result, an amorphous nanocolumnar film with ferromagnetic resonance frequency of greater than 5 GHz, high relative permeability of 44.9, and low loss factors of less than 1% up to 1 GHz was achieved.

Feasibility study of homojunction CIGS solar cells

The potential for high conversion efficiency of the homojunction Cu(In, Ga)Se2 (CIGS) solar cells was examined by device simulations and experimental approaches. The simulation results showed that many electrons in n-CIGS layers could compensate to some extent for the existence of interface states at i-ZnO/n-CIGS interfaces in the homojunction structure. In the case of using the partial electrolyte treatments of CIGS films to produce the n-type doping, the concentrations of the Cd dopants in the n-CIGS layer were 1016 cm-2. The conversion efficiency of 17.2% for this homojunction CIGS solar cell was obtained.